Chemokines are chemotactic cytokines, of molecular weight 6-15 kDa, that are released by a wide variety of cells to attract and activate, among other cell types, monocytes, macrophages, T and B lymphocytes, eosinophils, basophils and neutrophils. There are two major classes of chemokines, CXC and CC, depending on whether the first two cysteines in the amino acid sequence are separated by a single amino acid (CXC) or are adjacent (CC). The CXC chemokines, such as interleukin-8 (IL-8), neutrophil-activating protein-2 (NAP-2) and melanoma growth stimulatory activity protein (MGSA) are chemotactic primarily for neutrophils and T lymphocytes, whereas the CC chemokines, such as RANTES, MIP-1α, MIP-1β, the monocyte chemotactic proteins (MCP-1, MCP-2, MCP-3, MCP-4, and MCP-5) and the eotaxins (-1 and -2) are chemotactic for, among other cell types, macrophages, T lymphocytes, eosinophils, dendritic cells, and basophils.
The chemokines bind to specific cell-surface receptors belonging to the family of G-protein-coupled seven-transmembrane-domain proteins which are termed “chemokine receptors.” On binding their cognate ligands, chemokine receptors transduce an intracellular signal though the associated trimeric G proteins, resulting in, among other responses, a rapid increase in intracellular calcium concentration, changes in cell shape, increased expression of cellular adhesion molecules, degranulation, and promotion of cell migration. There are at least ten human chemokine receptors that bind or respond to CC chemokines with the following characteristic patterns: CCR-1 (or “CKR-1” or “CC-CKR-1”) [MIP-1α, MCP-3, MCP-4, RANTES] CCR-2A and CCR-2B (or “CKR-2A”/“CKR-2B” or “CC-CKR-2A”/“CC-CKR-2B”) [MCP-1, MCP-2, MCP-3, MCP-4, MCP-5]; CCR-3 (or “CKR-3” or “CC-CKR-3”) [eotaxin-1, eotaxin-2, RANTES, MCP-3, MCP-4]; CCR-4 (or “CKR-4” or “CC-CKR-4”) [TARC, MDC]; CCR-5 (or “CKR-5” OR “CC-CKR-5”) [MIP-1α, RANTES, MIP-1β]; CCR-6 (or “CKR-6” or “CC-CKR-6”) [LARC]; CCR-7 (or “CKR-7” or “CC-CKR-7”) [ELC]; CCR-8 (or “CKR-8” or “CC-CKR-8”) [I-309]; CCR-10 (or “CKR-10” or “CC-CKR-10”) [MCP-1, MCP-3]; and CCR-11 [MCP-1, MCP-2, and MCP-4].
In addition to the mammalian chemokine receptors, mammalian cytomegaloviruses, herpesviruses and poxviruses have been shown to express, in infected cells, proteins with the binding properties of chemokine receptors. Human CC chemokines, such as RANTES and MCP-3, can cause rapid mobilization of calcium via these virally encoded receptors. Receptor expression may be permissive for infection by allowing for the subversion of normal immune system surveillance and response to infection. Additionally, human chemokine receptors, such as CXCR4, CCR2, CCR3, CCR5 and CCR8, can act as co-receptors for the infection of mammalian cells by microbes as with, for example, the human immunodeficiency viruses (HIV).
The chemokines and their cognate receptors have been implicated as being important mediators of inflammatory, infectious, and immunoregulatory disorders and diseases, including asthma and allergic diseases, as well as autoimmune pathologies such as rheumatoid arthritis and arthrosclerosis (reviewed in: Carter, P. H., Current Opinion in Chemical Biology 2002, 6, 510; Trivedi et al., Ann. Reports Med. Chem. 2000, 35, 191; Saunders et al., Drug Disc. Today 1999, 4, 80; Premack et al., Nature Medicine 1996, 2, 1174). For example, the chemokine macrophage inflammatory protein-1 (MIP-1α) and its receptor CC Chemokine Receptor 1 (CCR-1) play a pivotal role in attracting leukocytes to sites of inflammation and in subsequently activating these cells. When the chemokine MIP-1α binds to CCR-1, it induces a rapid increase in intracellular calcium concentration, increased expression of cellular adhesion molecules, cellular degranulation, and the promotion of leukocyte migration.
In addition, demonstration of the chemotactic properties of MIP-1α in humans has been provided experimentally. Human subjects, when injected intradermally with MIP-1α, experienced a rapid and significant influx of leukocytes to the site of injection (Brummet, M. E., J. Immun. 2000, 164, 3392-3401).
Demonstration of the importance of the MIP-1α/CCR-1 interaction has been provided by experiments with genetically modified mice. MIP-1α −/− mice had normal numbers of leukocytes, but were unable to recruit monocytes into sites of viral inflammation after immune challenge. Recently, MIP-1α −/− mice were shown to be resistant to collagen antibody induced arthritis. Likewise, CCR-1 −/− mice were unable to recruit neutrophils when challenged with MIP-1α in vivo; moreover, the peripheral blood neutrophils of CCR-1 null mice did not migrate in response to MIP-1α, thereby demonstrating the specificity of the MIP-1α/CCR-1 interaction. The viability and generally normal health of the MIP-1α −/− and CCR-1 −/− animals is noteworthy, in that disruption of the MIP-1α/CCR-1 interaction does not induce physiological crisis. Taken together, these data lead one to the conclusion that molecules that block the actions of MIP-1α would be useful in treating a number of inflammatory and autoimmune disorders. This hypothesis has now been validated in a number of different animal disease models, as described below.
It is known that MIP-1α is elevated in the synovial fluid and blood of patients with rheumatoid arthritis. Moreover, several studies have demonstrated the potential therapeutic value of antagonism of the MIP-1α/CCR1 interaction in treating rheumatoid arthritis.
It should also be noted that CCR-1 is also the receptor for the chemokines RANTES, MCP-3, HCC-1, Lkn-1/HCC-2, HCC-4, and MPIF-1 (Carter, P. H., Curr. Opin Chem. Bio. 2002, 6, 510-525). Since it is presumed that the new compound of formula (I) described herein antagonizes MIP-1α by binding to the CCR-1 receptor, it may be that this compound is also an effective antagonist of the actions of the aforementioned ligand that are mediated by CCR-1. Accordingly, when reference is made herein to “antagonism of MIP-1α,” it is to be assumed that this is equivalent to “antagonism of chemokine stimulation of CCR-1.”
Recently, a number of groups have described the development of small molecule antagonists of MIP-1α (reviewed in: Carson, K. G. et al., Ann. Reports Med. Chem. 2004, 39, 149-158).